1. Field of the Invention
The present invention relates to a backlight module of a liquid crystal display and, said backlight module having indentation part to absorb shock or import energy and to prevent the light guide plate from cracking.
2. Description of Related Art
Generally, the precision electronics products have to pass some basic inspections before they enter the market so as to guarantee an acceptable extent of product quality as well as rights and interests of consumers. This is of course also true for notebook computers. Every notebook manufacturer certainly has a matured system of quality control in the production and inspection of devices so that the quality control can be implemented thoroughly. In particular, in the circumstance of a vigorously competitive market, the manufacturers tend to manifest the reliability of products by drawing up strict inspection criteria in order to gain the market identification. Therefore, each notebook computer has to pass a complete set of tests including those for endurance to shock and pressure, the opening and closing lifetime of the screen, high and low temperature environment, electric wave affection, static environment, severe operation, etc. Among the tests above-mentioned, the shock test is aimed to inspect the impact resistance of the interior of the notebook. By dropping the notebook vertically to a metal platform, the shock test can test the antishock capability of the notebook. In the shock test, strict scrutiny of the antishock capability of both the notebook body and the liquid crystal display device is carried out.
In the early stages of notebook computer testing, the requirement of shock endurance was comparatively low with respect to current criteria, hence the backlight module could pass the shock test without need for further refinement. However, more exacting standards developed since then have resulted in the lamp of the backlight module of the liquid crystal display device often breaking due to the impact of the light guide plate during the shock test. Thus, the original design of the backlight module can no longer pass the shock test. Therefore, current light guide plates are modified to have a pair of protrusions, which can be held by the corresponding indentation parts formed on the frame in order to prevent the light guide plate from impacting on the lamp. The trend of notebook computers to become increasingly compact has resulted in the need for the liquid crystal display devices to be made thinner. Hence, the thickness of the light guide plate of the backlight module, is correspondingly reduced. Simultaneously, the shock endurance testing for the notebook computer has become even stricter. Consequently, the thinned light guide plate with lower mechanical strength cannot endure that strong impact and, particularly, often cracks at the root of protrusions. The high scrap rate of the light guide plate is an economic burden for the manufacturers. Therefore, it was proposed in USP20030043312 to form a damping slit adjacent to the indentation part, as shown in FIG. 3. Because the lamp is located below the housing 100, a slit 120 with equal width is formed below the indentation part 110 of the housing 100 so that the structure strength around the indentation part 110 of the side frame is weakened, a buffer space for the deformation of the protrusion 130 caused by the impact of the light guide plate is provided, and the impact force can therefore be decreased. However, the width of the slot 120 is limited and must be less than the distance between the light guide plate and the lamp in order to mitigate the impact effectively and certainly prevent the lamp from being impacted by the light guide plate. However, in order to reduce the volume of the liquid crystal display device and enhance the lighting efficiency, the distance between the light guide plate and the lamp has become very short, so it is quite difficult in practice to make a mold for manufacturing such a narrow slit. Even though the mold can be made successfully, the lifetime of the mold is still very short because the structure strength of a narrow slit is weak and it can't endure a plastic injection process too many times, and thus again, overall manufacturing costs are too high.
Therefore, it is desirable to provide a housing for a backlight module and a backlight module using the same to mitigate and/or obviate the aforementioned problems.